Syphilis is an infectious, sexually transmitted disease that continues to be a major public health problem in the United States as well as other countries. Research on Treponema pallidum, the etiological agent of syphilis, has been hampered by the inability to successfully culture the spirochete to high yields in vitro for sustained periods of time. Although T. pallidum can be propagated in rabbit testes and purified in small quantities such procedures usually result in the loss of treponemal virulence. Recently, several investigators have sought to use recombinant DNA technology in an attempt to circumvent some of the difficulties associated with obtaining suitable quantities of T. pallidum components for experimental studies. In our laboratory we are attempting to clone and express in Escherichia coli and the genetic information encoding for T. pallidum cell surface and extracellular protein antigens. We are particularly interested in these proteins since they are the only treponemal proteins that are in direct contact with the infected host and thus may play an important role in pathogenesis. Presumably, a protective immune response would be targeted against such antigens. Our long term goal is to produce the cell surface and extracellular protein antigens in sufficient quantities so that their role in the pathogenesis of syphilis can be investigated and their applicability for use as improved serodiagnostic test reagents and/or potential vaccinogens can be evaluated. For our project period, we propose to do the following: (i) Murine monoclonal antibodies and rabbit polyclonal antibodies to the T. pallidum cell surface and extracellular protein antigens will be generated. (ii) E. coli clones expressing the protein antigens of interest will be identified and strategies to maximize expression of these proteins in E. coli will be developed, thus facilitating their purification. We have on hand a library of T. pallidum genomic DNA that was constructed using a plasmid vector. We have developed techniques to identify and characterize E. coli clones expressing treponemal protein antigens and to produce the proteins in sufficient quantities that allowed for purification. (iii) a variety of experiments aimed at determining the biological significance of the cell surface and extracellular T. pallidum protein antigens will be conducted.